Hydrocarbon conversion



5 amps/we 28, 1943- c. L. THOMAS 2,337,630

HYDROCARBON CONVERSION Filed Feb. '28. 1941 FPACTIONA TTOB 29 s L l REACTION I CHAMBER I 28 FURNACE 55' STOCK T H Z4 Z5 @orneg.

Patented Dec- 2s, 1943 .HYDROCARBON CONVERSION Charles L. Thomas, Chicago, 111., assignor to Universal Oil Products Company, Chicago, EL, a

corporation of Delaware Application February 28, 1941, Serial No. 380,964

1 Claim. (Cl. 19652) This application is a continuation-impart of my co-pending application, Serial No. 356,596, filed September 13, 1940.

This invention relates to a process for the conversion of hydrocarbon oil into substantial yields of gasoline and more specifically to animproved process combining catalytic with thermal cracking wherein charging oil and selected insufficiently converted hydrocarbons from both thermal and catalytic cracking are subjected to catalytic cracking and the residual portion of the insufficiently converted hydrocarbons from both thermal and catalytic cracking are subjected to thermal cracking.

Catalytic cracking as ordinarily conducted does not employ recycling of insufiiciently converted products to the conversion zone because, as has been found, such insufliciently converted hydrocarbons contain a certain amount of undesirable material, the tendency of which is to deposit great amounts of a carbonaceous deposit upon the catalyst particles if recycled to the catalyst zone. This results in a more rapid lowering of the catalyst activity than is encountered when clean unconverted oils are passed in contact with such catalysts. In order to reduce the formation of carbonaceous substances during conversion so that shorter reactivation times and] or lower peak reactivatingtemperatures may be accomplished, it is usual to pass the hydrocarbon oil in contact with the catalyst only once and then to crack thermally the insufficiently converted oils in a thermal cracking system. In a process employing both thermal and catalytic cracking in the manner above mentioned, the yield and antiknock value of the gasoline product are good but are not as good as one might expect from a process boiling in the same range asthe charging stock is quite amenable to further catalytic cracking since it contains hydrocarbons similar in nature to those of the original charge. 0n the other hand,

theproduct boiling between the gasoline range and the charging stock range is usually more refractory since it comprises substantially converted of the coke forming constituents present in the original fraction have been removed.

Therefore, the object of this invention is to combine a catalytic and a thermal cracking treat ment in a novel and useful manner so that the charge to the catalytic treatment comprises a fresh hydrocarbon oil charge, heavyconversion products from the catalytic step, and intermediate insufiiciently converted hydrocarbons from the thermal step; and the charge to the thermal treatment comprises intermediate conversion products from the catalytic step and heavy insufficiently converted hydrocarbons from the thermal step.

In one specific embodiment this invention comprises supplying heated fresh charging oil and heated insufliciently converted oils formed as hereinafter set forth to a catalytic conversion zone, fractionating the resultant conversion products to separate gasoline boiling range hydrocarbons, light reflux condensate, and heavy reflux condensate, returning said heavy reflux condensate to said catalytic conversion zone as hereinbefore set forth, supplying said light reflux condensate together withheavy insuificiently converted hydrocarbons formed as hereinafter set forth to a non-catalytic conversion zone, separating the resultant products into non-vaporous liquid residue and vaporous reaction products, fractionating said vaporous reaction products to separate gasoline boiling range hydrocarbons, light insufficiently converted hydrocarbons, and

' heavy insufliciently converted hydrocarbons, supplying said light insufli'ciently converted hydrocarbons to said catalytic conversion zone as hereinhefore set forth, and returning said heavy insufiiciently converted hydrocarbons to said thermal conversion zone.

l The accompanying drawing shows diagrammatically in side elevation one specific arrangement of the apparatus which may be used within the broad scope of this invention.

Referring now to the drawing, fresh charging oil which may comprise any desired petroleum distillate boiling substantially above the gasoline range, preferably heavy gas oil or wax distillate, is introduced through line I containing valve 2 intopump 3, line 4 containing valve 5, and is thereafter commingled with insufliciently converted hydrocarbons formed. as hereinafter set forth. The resulting mixture is heated to the desired conversion temperature in heating coil 6 disposed in furnace I, and-the heated material is conducted through line 8 containing valve 9 into reactor ll wherein it is contacted with a catalytic F., and the pressures may range from substantially atmospheric to 200 pounds or more per square inch. Reactor I may comprise, for example, a chamber of the heat exchange type to which heat may be supplied or from which heat may be removed by means of a fluid in indirect heat exchange. On the other hand, if desired, reactor l0 may comprise a cylindrical vessel insulated in such a manner that the reactions occurring therein are substantially adiabatic.

Catalysts which have been found to be effective in the catalytic cracking of hydrocarbons may comprise pellets or granules of silica or other siliceous and refractory materials composited with compounds selected from the group consisting of alumina, zirconia, and thoria. In addition, the hydrosilicates of alumina, acid treated clays, or the like, have also been found to be effective in the cracking treatment of hydrocarbons. Although the catalysts above recited are generally considered to be the preferred catalysts their use is not to be construed as a limiting feature, for various other catalysts .well known to those in the art may be employed within the broad scope of the invention.

In the catalytic cracking of hydrocarbons relatively large amounts of carbonaceous substances are formed which deposit upon the catalytic material thereby reducing its active surface and necessitating reactivation at periodic frequent intervals. The invention contemplates reactivating the used catalytic material in the usual manner, such as, for example, by passing oxygen-containing reactivating gases in contact with the used catalytic material and removing carbonaceous substances as combustion gases along with the spent reactivating gases. It is desirable, therefore, in order that the operation may be carried out as a continuous process to employ at least two reactors and in some instances more than two reactors so that while the catalytic material in one reactor is being used for effecting conversion of the hydrocarbon reactants the catalytic material in the other or others may be undergoing reactivation.

The reaction products leaving chamber ID are conducted through line H containing valve [2 into fractionator l3 which is operated at substantially the same or at a reduced pressure relative to chamber wherein gasoline boiling range hydrocarbons are separated from higher boiling hydrocarbons. The gasoline hydrocarbons are conducted in the vaporous state through line l4 containing. valve and may be thereafter cooled, condensed, and separated from lig t gases by y well known means, not shown. A portion of the condensed liquid gasoline boiling range hydrocarbons may be returned to fractionator l3 as a cooling and refluxing medium by well known means, not shown, and the remaining portion of .into'pump-IB and line 19 containing valve 20.

and is-thereafter commingled with the fre'shhydrocarbon oil in line 4 as hereinbefore set forth.

Light reflux condensate, which is separated and condensed in through line-2| containing valve 22 into pump 23 fractionator I3, is conducted and line 24 ,containing valve 25, and is thereafter commingled with heavy conversion products formed as hereinafter set forth. The resulting mixture is heated in coil 26 disposed in furnace 21 at a pressure and to a temperature at which substantial-cracking occurs, heat being supplied by furnace 21.

The conversion products are directed through line 28 containing valve 29 into communicating reaction chamber 30 wherein further conversion occurs. The temperatures employed in this thermal conversion step may range, for example, from 600 to 1200 F., preferably from 800 to 1000 F., and the pressures may range, for example, from 100 to 1000 pounds or more per square inch. Reaction chamber 30 is preferably insulated to reduce radiation losses therefrom, although no insulation appears in the drawing. The conversion products leaving reaction chamber 30 are conducted through line 31 containing valve 32 into vaporizing and separating chamber 33. Chamber 33 is preferably maintained at a pressure and temperature lower than that employed in reaction chamber 30 ranging, for example, from 700 to 1000 F. and from substantially atmospheric to 200 pounds or more per square inch.

In chamber 33 vaporous liquid residue is separated from the vaporous conversion products and is withdrawn through line 34 containing valve 35 and may be subjected to any desired further treatment. The vaporous conversion products leaving chamber 33 are conducted through line 36 containing valve 31 into fractionator 38 wherein gasoline boiling range hydrocarbons, intermediate conversion products, and heavy conversion products. are separated. The gasoline boiling range hydrocarbons are conducted through line 39 containing valve 40 and are thereafter cooled, condensed, and separated from the gaseous hydrocarbons by any well known means, not shown. A portion of the condensed gasoline boiling range hydrocarbons may be returned to fractionator 38 as a cooling and refluxing medium by well known means, not shown, and the remaining portion is recovered and may be subjected to any further treatment. Intermediate conversion products separated and condensed in fractionator 38 are conducted through line 4! containing valve 42 into pump 43 and line 44 containing valve 45 and are thereafter commingled with the fresh charging oil and with the heavy reflux condensate from the catalytic step as hereinbefore set forth. The heavy conversion products separated and condensed in fractionator 3B are conducted through line 46 containing valve 4'! into pump 48 and line 49 containing valve 50 and are thereafter commingled in line 24 with the light reflux condensate from the catalytic conversion step.

An example of one specific operation of the process as it may be accomplished in an apparatus such as that illustrated and described above is approximately as follows: Charging oil comprising a 28 A. P. I. gravity Mid-Continent heavy gas oil is commingled with insufiiciently converted hydrocarbons formed as hereinafter set forth and the resulting mixture is contacted with a cracking I catalyst comprising substantially silica, alumina and zirconia at a temperature of 900 F. and at a pressurepf30 pounds per square inch. The resulting ciinifersion products are fractionated to separate gasoline boiling range hydrocarbons and light hydrocarbon gases, light reflux condensate, and heavy reflux condensate. The gasoline and light gases are recovered and the heavy reflux condensate is comminglecl with carbons.- I a The resultant conversion products are supplied reflux condensate together with insufllclently converted hydrocarbons formed as hereinafter set forth is supplied to a thermal cracking step wherein it is maintained at a temperature of 900 F. and at a pressure of 200 pounds per square inch for a suflicient length of time to produce substantial yields of gasoline boiling range hydrotoa vaporizing and separating zone maintained at a temperature oi. 800 F. and at a pressure of 50 pounds per square inch wherein the nonvaporous liquid residue is separated from the vaporous conversion products and is recovered. The vaporous conversion products are supplied to a fractionator wherein gasoline boiling range hydrocarbons and hydrocarbon gases, intermediate conversion products, and heavy conversion products are separated. The gasoline and the hydrocarbon gases are recovered. The intermediate convmsion productsare commingled with the fresh charging oil and with the heavy reflux condensate from thecatalytic conversion step and are subjected to treatment as hereinbefore described. The heavy conversion products are commingled with the light reflux condensate from the catalytic conversion step and are subjected to thermal treatment as hereinbeiore described.

In this manner of operation one may obtain a ass'mso the fresh reed and returned to the catalytic conversion step as hereinbeiore set forth. The light 37.2% yield c179 octane number gasoline in the catalytic conversion step, a 26.2%. yield of '10 octane. number gasoline in the thermal conversion step, and a 20.2% yield of residuum from .the thermal conversion step, the balance being principally gas, carbonaceous deposits, and loss.

I claim as my invention:

A conversion process which comprises catalyticall'y cracking a relatively heavy hydrocarbon charging oil, iractionating the resultant products to separate therefrom a gasoline distillate, a heavy reflux condensate boiling in substantially the same range as said charging oil and a lighter reflux condensate boiling intermediate said distillate and heavy reflux condensate, returning said heavy reflux condensate to the catalytic cracking step, subjecting said lighter reflux condensate to non-catalytic thermal cracking, tractionating the vaporous products oi. the thermal cracking independently oi the products of the catalytic cracking to separate therefrom a heavy reflux condensate and a lighter reflux condensate amenable to catalytic cracking, returning the last-named heavy reflux condensate to the thermal cracking step. and supplying the last-named lighter reflux condensate to the catalytic cracking step for treatment therein together with the charging oil and the first-mentioned heavy reflux condensate.

'cnmmsn'rnoms. 

